biomass and energy transfer through ecosystems pt 2

what happens to light energy that fall on a plant leaf?

• only convert 1-3% of light energy into chemical energy

how is energy lost between the sun and producers?

• reflection of light

• transmission of light

• light of incorrect wavelength for absorption of chlorophyll

• evaporation of water from leaf

• heat loss as biproduct of respiration

how much energy is lost between trophic levels?

around 90%

where is energy lost between trophic levels going?

• not ingested all of it

• not digested or assimilated

• excreted

• lost as heat from respiration

how is energy lost between producers and consumers?

• lots can’t be eaten by primary consumer e.g. roots

• producers have cellulose walls which can’t be digested as consumers don’t have the enzyme cellulase

• much material is egested

• energy used by gut bacteria in consumer

• energy lost as heat as biproduct of respiration

how is energy lost between consumers?

• excretion - urine

• egestion - faeces

• respiration - heat loss

• not all the animal/plant is eaten (e.g. bones)

why does biomass decrease between trophic levels?

because chemical energy stored in biomass is lost between trophic levels

why is biomass often used to measure energy transfer?

Because energy is stored in the chemical bonds of biomass.

why are food chains limited in length?

Too much energy is lost at each trophic level

what eventually makes very high trophic levels unviable?

The energy required for foraging exceeds the energy gained from food

why do primary consumers often lose more energy in their faeces than secondary consumers?

The primary consumers can't digest the cellulose in the plants so it stays in their fasces and so more energy is lost

why do secondary consumers often lose more energy in respiration than primary consumers?

• Movement - they have to do lots of exercise to catch their pray

• Thermoregulation - to maintain our temperature (bigger animals)

what does calculating energy efficiency allow you to do?

• allows you to see the productivity of a food chain

• e.g. the rate of biomass production/the amount of biomass produced per unit time through a food chain

what is the productivity of a producer called?

primary productivity

what is gross primary production (GPP)?

Total amount of energy converted into chemical energy by producers as a result of photosynthesis

what is net primary production (NPP)?

• the actual rate of production of new biomass by the producers

• represents the biomass available for consumers to eat

what is the equation for Net Primary Production (NPP)?

net primary production (NPP) = gross primary production (GPP) - respiratory energy loss (R)

what is the ecological efficiency equation?

ecological efficiency = energy (or biomass) available after transfer/ energy (or biomass) available before the transfer x100

what is a decomposer?

organisms that consume any waste material

what can GPP/NPP vary because of? why?

• environmental temp

• day length

• light intensity

• availability of soil mineral

All of above affect species of plant that grow and their density and so affect GPP/NPP

how can we increase NPP by increasing the productivity of producers?

• greenhouses - control temp, CO2 conc (photosynthesis)

• Irrigation - ensures enough water (photosynthesis)

• Selective breeding/genetic modification - e.g. decreased stem length to prevent wind damage; make plants produce insecticides to kill pests

• Pesticides (maintain healthy plants and so maximise productivity)

• Fungicides (maintain healthy plants and so maximise productivity)

• Herbicides (maintain healthy plants and so maximise productivity)

• Crop rotation - maintains optimum mineral content of soil

• Monoculture - prevents competition for things like soil minerals or space with unwanted species

how can we increase secondary productivity (consumer to consumer)?

• Harvesting animals at an earlier age

• Steroids to increase growth rates

• Selective breeding to produce fast growing organisms, higher egg production, increased milk yield

• Antibiotic treatments to prevent energy loss to pathogens

• Temperature control (in barns)

• Restriction of movement (in barns)